The invention relates to a special colostrum and a method of manufacturing it.
Bovine colostrum collected within 30 hours of calving contains high levels of immunoglobulins G, A, and M. The substance also contains other proteins that make it ideal for providing calves with a passive immunity, especially against enteropathogenic germs, during their first few days. This property of the colostrum has led to the development of several methods of isolating the immunoglobulins for use against gastro-intestinal disorders in humans in particular.
German C 2,813,984 and C 3,432,718, European B 102,831, and U.S. Pat. Nos. 4,051,235, 4,784,850, and 4,834,974 for example describe the manufacture from colostrum of preparations that contain immunoglobulins. These preparations also contain some other proteins. What is common to all, however, is that they are made from colostral serum (whey) once the casein has been acid or enzyme precipitated and separated. The casein must always be eliminated when the colostrum is to be either filtered sterile or ultrafiltered.
Bovine colostrum is about 12% protein and contains cell particles and a large number of bacteria.
There are between 10.sup.6 and 10.sup.8 germs/ml in raw colostrum as against between 10.sup.3 and 10.sup.4 germs/ml in regular cow's milk, Pasteurization for 15 to 40 seconds at 71.degree. to 74.degree. C. or for 1 to 4 seconds at 85.degree. to 90.degree. C. for example reduces the count of pathogenic germs by 1 to 2 powers of ten, which still represents a high level of bacteria. These germs can multiply while the substance is in storage and cause severe side effects especially when it is employed to treat gastro-intestinal disorders.
U.S. Pat. No. 3,911,108 describes sterilizing colostrum and its derivatives with .beta.-propiolactone. Another approach for example is to treat the colostrum with gamma radiation. Both methods, however, tend to denature the proteins to some extent.
Filtration sterilization, the simplest and most effective method of eliminating the bacteria and the method that best protects the proteins, cannot be employed with colostrum because the casein immediately clogs up the filter. All methods that are intended to produce a preparation that can be filtered sterile or ultrafiltered accordingly start from the optionally defatted whey. The casein is acid or enzyme precipitated and centrifuged out while the whey is being prepared. The whey or its isolated fractions can then be ultrafiltered and filtered sterile.
German C 2,813,984 expressly asserts that skimming and clarification (casein precipitation) must be very extensive to prevent clogging the filter and ultrafilter later.
Eliminating the casein by precipitation, however, has serious drawbacks with respect to using or purifying the colostrum later.
1. As much as 40% of the immunoglobulins can be trapped along with the casein in the precipitate and coprecipitate and lost.
2. Centrifuging out the precipitate is complicated and expensive, especially considering the yield of immunoglobulins.
3. Casein itself has beneficial therapeutic properties that in particular augment the actions of the immunoglobulins in gastro-intestinal disorders. Opiate-like substances are released from the casein and help suppress peristalsis and promote the resorption of electrolytes and water. These activities have also been ascribed to the intact casein (B. Recker, Physis [January 1989], 32).
It is generally desirable to alter the protein composition of the colostrum as little as possible because it is already ideal for the prevention and treatment of gastro-intestinal infections and disorders. In addition to the immunoglobulins and casein for instance, such proteins as lysozyme, lactoferrin, and the peroxidases carry out significant functions in the defense against bacterial infections. A majority of these important proteins, however, are either separated out or inactivated by casein precipitation and pasteurization.
The object of the present invention is accordingly a method of removing bacteria from colostrum by filter sterilization that will retain as many of the protein constituents of the original colostrum as possible.
It has surprisingly been discovered that colostrum can, without previously removing the casein, be filtered clear and sterile by adjusting it, optionally defatted, to a pH less than 3.5. Although the casein precipitates at a pH of 5 to 4, it will return to solution as the pH continues to drop. The acidic solution differs so extensively from the original colostrum that it can be filtered sterile.
The colostrum so acidified can be restored to its original pH before being filtered. As the acidity is neutralized, the casein will precipitate again at a pH of 4 to 5 and return to solution at approximately 5.5. The resulting colostrum is surprisingly even somewhat easier to filter than the defatted acidic colostrum at a pH of less than 3.5.
When decreasing the pH it is important to allow the casein to remain precipitated only briefly and to continue lowering the pH until the casein returns to solution. Preferably, the colostrum is substantially continuously acidified. If the casein remains precipitated too long and is returned too late to solution, the colostrum will be definitely more difficult to filter.
In one preferred embodiment of the invention the colostrum is defatted by measures that are in themselves known and diluted with a sodium chloride solution to 20 grams of protein per liter. Hydrochloric acid is added rapidly to adjust the pH of the colostrum to 2.0 to 3.5 and preferably 2.8 to 3.2, until the precipitate that accompanies the acidification returns to solution. The temperature should not increase beyond 45.degree. C. during the acidification to prevent denaturing the immunoglobulins.
The colostrum's pH can optionally be restored to its original value immediately or later by adding sodium hydroxide solution. As the pH increases, the casein will temporarily precipitate again and immediately return to solution.
Once the defatted colostrum has been subjected to the foregoing treatment, it can easily be filtered sterile or ultrafiltered by known methods. It can be filtered clear through a depth filter for example. The colostrum so clarified can then be filtered sterile through either a membrane or a depth filter. The defatted colostrum can also be ultrafiltered or dialyzed before or after being filtered sterile.
The material can be filtered even more easily if such filter aids as Hyflo Supercell for example are added.
The filtered-sterile defatted colostrum is preferably adjusted to 20 to 70 grams of protein per liter, although it can also be concentrated to 120 g/l. The concentration of lactose can also be decreased by dialysis and the ionic environment adjusted to make the resulting preparation especially appropriate for treating gastrointestinal disorders. The filtered-sterile defatted colostrum can also be freeze-dried or fractionated into its protein constituents.
Although the filtration is preferably carried out with defatted colostrum, the method in accordance with the invention is also appropriate for colostrum that has not been defatted. The rate of filtration is admittedly definitely lower than that of defatted colostrum but still substantially above that of colostrum that has not been acid treated.